Someone else will need to provide a definitive answer, I have never used one.

My understanding is once you connect an external eSATA HDD, the recordings will be spit between the internal and external, and removing the external will result in loss of recordings, until it is reconnected. Should the external HDD ever fail, all recordings will be lost.

Thanks, and yes, it's a Premiere.
If I go with the WD My Book AV DVR Expander 1 TB USB 2.0/eSATA External Hard Drive and unplug it at any time, will I loose my recordings or no?

On the original S3, there was an eSATA jack on the back panel that wasn't enabled.

They were going to do that in a later OS update.

In the meantime people figured out how to hack the software to get it to use that jack for adding an external drive, and used several differernt brands and models, so when TiVo got around to adding that feature in their own software upgrade, they had to grandfather in accepting any old model of drive.

But starting with the later S3s, the HD and HD XL, they have a very short list of acceptable WD hard drive models with which they work, so when you buy the 500GB or 1TB WD external with the TiVo logo on the box you can be sure that the model number of the drive inside is on that short list.

If you try to use a model that's not on that list, it won't accept it.

Once you hook up an external, everything recorded after that it spread across both drives so you need both drives working for the TiVo to work and play back those shows.

If the external goes bad you lose everything recorded since it was added.

It's generally accepted that the odds of one of the two drives going bad are added together when there's more than one.

If you want more space in a Premiere, start looking for a WD20EURS at around $100 and go read the upgrading Premiere drives with jmfs thread.

And don't use a GigaByte brand motherboard to do the upgrade without talking to me first and don't boot into Windows with the Premiere's drive attached.

When you use jmfs, you boot with the jmfs cd, which you make by downloading the image and burning it as an image to a cd-r.